Indira Gandhi Institute of Technology, Sarang Dhenkanal-759146

Partha sarathi Parhi(2014), presented a paper on ‘Stabilisation of expansive soil using alkali activated fly ash’

This research work presents the efficacy of sodium based alkaline activators and class F fly ash as an additive in improving the engineering characteristics of expansive Black cotton soils. Sodium hydroxide concentrations of 10, 12.5 and 15 molal along with 1 Molar solution of sodium silicate were used as activators. The activator to ash ratios was kept between between 1 and 2.5 and ash percentages of 20, 30 and 40 %, relatively to the total solids. The effectiveness of this binder is tested by conducting the Unconfined compressive strength (UCS) at curing periods of 3,7 and 28 days and is compared with that of a common fly ash based binder, also the most effective mixtures were analysed for mineralogy with XRD. Suitability of alkaline activated fly ash mix as a grouting material is also ascertained by studying the rheological properties of the grout such as, setting time, density and viscosity and is compared with that of common cement grouts. Results shows that the fluidity of the grouts correlate very well with UCS, with an increase in the former resulting in a decrease in the latter.

Dilip Shrivastava, A K Singhai and R K Yadav (2014) presented a research paper on the effect of lime and rice husk ash on engineering properties of black cotton soil. Black Cotton Soils exhibit high swelling and shrinking when exposed to changes in moisture content and hence have been found to be most troublesome from engineering considerations. This behavior is attributed to the presence of a mineral montmorillonit. The wide spread of the black cotton soil has posed challenges and problems to the construction activities. To encounter with it, innovative and nontraditional research on waste utilization is gaining importance now a days. Soil improvement using the waste material like Slags, Rice husk ash, Silica fume etc., in geotechnical engineering has been in practice from environmental point of view. The main objective of their study was to evaluate the feasibility of using Rice Husk Ash with lime as soil stabilization material. A series of laboratory experiment has been conducted on 5% lime mixed black cotton soil blended with Rice Husk Ash in 5%, 10% 15% and 20% by weight of dry soil. The experimental results showed a significant increase in CBR and UCS strength. The CBR values increases by 287.62% and UCS improved by30%.The Differential free swell of the black cotton soil is reduced by 86.92% with increase in Rise Husk Ash content from 0% to 20% respectively. From their investigation it could be concluded that the Rice Husk Ash has a potential to improve the characteristics of black cotton soil.

METHODOLOGY ADOPTED

In order to achieve the above objective, the black cotton soil has been arbitrarily reinforced with red mud. So the suitability of red mud is considered to enhance the properties of black cotton soil. A cycle of experiments such as Liquid limit test, Plastic Limit Test direct shear test, and unconfined compressive strength and was carried out on black cotton soil.

Tests carried out on materials :-

1. PARTICLE SIZE ANALYSIS
→1 Kg of the soil sample was taken and was sieved through a series of sieves i.e. 4.75mm,2.36mm,1.00mm,600 micron,425 micron,300 micron,212 micron,150 micron,75 micron.
→The mass retained on each sieve was weighed and the particle size graph was drawn.

2. PIPETTE ANALYSIS
→25 gm/50gm of the soil sample passing through 75 micron sieve was taken and was mixed with 25ml/50ml of sodium hexasulphonate.
→It was then mixed with water to form 500ml/1000ml
→ A 10ml pipette was used to withdraw a fixed sample from a fixed height at regular intervals i.e. 30sec,1min,2 min,4 min,8 min,15 min,30 min,1hr,2 hr,4 hr,8 hr,16 hr,24 hr.
→ The size of particles settled and percentage finer was obtained from the following formula:-

Factor F =10⁵[3000*ȵ/ (G-1)*ɣ_w]

=>F=1476

Diameter of the particle D =10^-5F [10/t] ^0.5

N= [M_D-(m/V)]/ {M_d/V} *100

Where V=Volume of suspension =1000ml/500ml

m=Mass of dispersing agent present in a volume of 50ml/25ml =2g/1g

M_d=Mass of sample taken =50g/25g

M_D=Dry mass of sample in container/volume of pipette

1. 
   SPECIFIC GRAVITY ANALYSIS
   →The material whose specific gravity is to be determined is sieved through 425 micron sieve.
   →2-3 no’s of density bottles were taken and were cleaned thoroughly.
   → Weight of empty bottle (M₁), weight of bottle + dry soil (M₂), weight of bottle + dry soil + water and weight (M₃) of bottle + water (M₄) was taken.
   → Now specific gravity was determined from the following formula:-
   Specific gravity (G) = (M2-M₁)/ [(M₂-M₁)-(M₃-M₄)]
   → The average of those values was taken.
   

4.ATTERBERG LIMITS DETERMINATION
→120gm of the soil sample passing through425 micron sieve was taken and water was added to it.
→The liquid limit of was determined by using Cassagrande apparatus and the water content corresponding to 25 blows was taken as the liquid limit
→The plastic limit was determined by rolling a ball of the sample to a thin thread of dia 3mm and the water content corresponding to this state was taken as the plastic limit

5 DIRECT SHEAR TEST

Direct shear test was conducted on both the soil sample as well as on the red mud using shear box apparatus to find out the shear strength of soil.A specimen is placed in shear box which has two stcked rings to hold the sample.A confining stress is applied vertically to the specimen and the upper ring is pulled laterally until the sample fails.The load applied and the strain induced is recorded at frequent interval to determine the stress-strain curve for each confining stress.Soil cohesion (c) and angle of internal friction was determined.The result of the test was plotted with stress on y-axis and confining stress on x-axis.

6 UNCONFINED COMPRESSIVE STRENGTH

In order to determine the strength of soil unconfined compression test was conducted on the soil sample.Undisturbed specimen was cut from the tube sample and then they are loaded in compression,recording load and deflection measurement.

q_u =

where qu=Unconfined compressive strength

P=compressive force

A=Cross sectional area

A = =

=

L₀=initial length of the specimen

L=Final length of the specimen at which failure occurs


CHAPTER 3

OBSERVATION OF BLACK COTTON SOIL

ATTERBERG LIMIT ANALYSIS

1.LIQUID LIMIT DETERMINATION

No. of Container	BPL 1	BPL 2	BPL 3
No. of blows	52	40	15
Mass of Container	10.220	13.990	13.300
Mass of container+Wet soil	16.250	26.800	24.080
Mass of container+Dry soil	14.390	22.600	20.050
Water content	44.6	48.78	59.70

Hence liquid limit of black cotton soil=54%

2. PLASTIC LIMIT

Container No	BPL 1	BPL 2	BPL 3
Mass of container +wet soil	17.370	18.010	21.110
Mass of container +dry soil	16.830	17.370	20.20
Mass of container	14.330	14.070	15.880
Water content	21.34	19.39	21.06

Hence plastic limit was found to be 20.59%

Shrinkage limit

Similarly Shrinkage limit was found to be 9.465%

Plasticity index =liquid limit-plastic limit=33.41%

Specific Gravity

Specific gravity of the black cotton soil was found to be 2.35

Maximum dry density

Mass of mould +compacted soil	3.690	3.850	3.930	3.840
Mass of mould	2.010	2.010	2.010	2.010
Mass of compacted soil	1.68	1.749	1.92	1.83
Bulk density	1.732	1.803	1.98	1.88
Dry density	1.48	1.463	1.582

Water content determination

Mass of container	14.420	14.840	15.930	17.050
Mass of container+wet soil	19.360	22.100	23.440	30.040
Mass of container+dry soil	18.640	20.730	21.930	27.080
Water content	17.06	23.25	25.17	29.51

So from the above table maximum dry density =1.582gm/cm³

And optimum moisture content was found to be 25.17%

PIPETTE ANALYSIS

Elapsed time(min)	Temp(in degree)	Factor(F)	D(mm)	Bottle+ dry mass	Mass of bottle	Dry mass of soil	MD	N%	N’
1/2	30	1230	0.055	16.810	17.270	0.46	0.046	88	5.61
2	30	1230	0.027	15.600	16.020	0.42	0.042	80	5.10
4	30	1230	0.019	17.200	17.620	0.42	0.042	80	5.10
15	30	1230	0.010	15.430	15.750	0.32	0.032	60	3.82
30	30	1230	0.007	13.190	13.460	0.27	0.027	50	3.19
120	30	1230	0.0035	12.280	12.520	0.24	0.024	44	2.80
240	30	1230	0.0025	11.570	11.770	0.20	0.020	36	2.29
480	30	1230	0.0017	10.070	10.260	0.19	0.019	34	2.17
1440	30	1230	0.0010	11.820	11.920	0.10	0.010	16	1.53

Specific Gravity G=2.35

H_e=10cm
Volume of pipette =10ml
At room temp (27⁰C) µ =0.00855
Factor F =10⁵[3000*ȵ/ (G-1)*ɣ_w] =>F=1476
Diameter of the particle D =10^-5F [10/t] ^0.5

FOR % FINER

V=Volume of suspension =1000ml
m=Mass of dispersing agent present in a volume of 50ml =2g
M_d=Mass of sample taken =50g
M_D=Dry mass of sample in container/volume of pipette
N= [M_D-(m/V)]/ {M_d/V} *100
N= [(Dry mass/10) – (1/500)]*2000

PARTICLE SIZE ANALYSIS

Sieve size	Actual mass retained		% mass retained	Cumulative % mass retained	% finer
4.75 mm		0	0	0	100
2.00 mm		88.861	7.89	7.89	92.11
1.00 mm		116.24	14.35	22.24	77.76
600 micron		46.14	5.696	27.936	72.064
425 micron		47.44	5.85	33.786	66.214
300 micron		29.89	3.69	37.476	62.524
212 micron		34.41	4.24	41.716	58.284
150 micron		25.79	3.183	44.899	55.101
75 micron		33.82	4.17	49.069	50.931

From the graph Gravel=7.09%

Sand=40.11%

Silt=52.8%

Clay=17.8%

Uniformity coefficient=245.45 and coefficient of curvature=0.33

As D₆₀ =0.27

D₃₀ =0.01

D₁₀ =0.0011

C_u = D₆₀ / D₁₀ =245.45

C_c = ( D₃₀ × D₃₀)/ D₁₀ × D₆₀=0.33

Direct Shear Test

Test no	Normal Stress	Shear stress at failure	Shear displacement at failure in mm
1	0.5	0.644	0.75
2	1.5	1.958	2.25
3	2.5	2.003	2.30

Graph was plotted between normal stress and shear stress and from the graph

Angle of internal friction was found to be 35⁰ and c or cohossion value was found to be 0.25.

Unconfined Compressive Strength

Deformation in mm	strain	Axial strain in %	Area(cm2)	Proving ring dial reading	Applied axial load in Kg	Stress in Kg/cm2
0	0	0	9.62	0	0	0
0.5	0.0067	0.67	9.684	17	6.02	0.621
1	0.0135	1.35	9.751	24	8.51	0.872
1.5	0.020	2.0	9.816	31	10.99	1.12
2	0.027	2.7	9.886	33	11.70	1.183
2.5	0.033	3.3	9.948	38	13.47	1.354
3	0.040	4	10.02	47	16.67	1.663
3.5	0.047	4.7	10.09	52	18.43	1.82
4	0.054	5.4	10.169	56	19.85	1.95
4.5	0.061	6.1	10.24	61	21.63	2.112
5	0.067	6.7	10.31	64	22.69	2.2
5.5	0.074	7.4	10.388	67	23.75	2.28
6	0.081	8.1	10.467	69	24.46	2.33
6.5	0.087	8.7	10.536	70.5	25	2.37
7	0.094	9.4	10.618	70.7	25	2.35

A graph was plotted between σ and ε.The maximum stress from this curve gave the value of unconfined compressive strength = q_u= 2.37Kg/cm²

=232.497KN/m²

Shear strength c= q_u/2 =1.185 Kg/cm²

=116.248KN/m²

OBSERVATION OF RED MUD

ATTERBERG LIMIT ANALYSIS

1.LIQUID LIMIT DETERMINATION

No. of Container	BPL 1	BPL 2	BPL 3	BPL 4
No. of blows	7	21	17	5
Mass of Container	17.00	16.700	8.000	16.720
Mass of container+Wet soil	21.630	21.940	12.720	30.200
Mass of container+Dry soil	20.650	20.690	11.77	27.060
Water content	26.84	25.05	25.19	30.36

Hence liquid limit of red mud=26%

2. PLASTIC LIMIT

As plastic limit could not be determined.Hence red mud is non plastic.

Shrinkage limit

Similarly Shrinkage limit was found to be 22.5%

Plasticity index =liquid limit-plastic limit=3.5%

Specific Gravity

Specific gravity of the red mud was found to be 2.924

Maximum dry density

Mass of mould +compacted soil	4.050	4.370	4.350
Mass of mould	2	2	2
Mass of compacted soil	2.050	2.370	2.350
Bulk density	2.055	2.376	2.36
Dry density	1.758	2	1.952

Water content determination

Mass of container	13.350	13.830	14.050
Mass of container+wet soil	21.530	27.330	28.280
Mass of container+dry soil	20.350	25.240	25.820
Water content	16.85	18.31	20.90

So from the above table maximum dry density =2gm/cm³

And optimum moisture content was found to be 18.31%

PIPETTE ANALYSIS

Elapsed time(min)	Temp(in degree)	Factor(F)	D(mm)	Bottle+ dry mass	Mass of bottle	Dry mass of soil	MD	N%	N’
1/2	30	1210	0.055	17.400	17.200	0.2	0.02	36	1.135
4	30	1210	0.019	14.210	14.070	0.14	0.014	24	0.756
8	30	1210	0.013	11.700	11.610	0.09	0.009	14	0.441
10	30	1210	0.012	14.110	14.020	0.09	0.009	14	0.441
120	30	1210	0.003	10.150	10.080	0.07	0.007	10	0.315
195	30	1210	0.0027	10.240	10.200	0.04	0.004	4	0.126
320	30	1210	0.0021	14.860	14.830	0.03	0.003	2	0.063
1440	30	1210	0.0010	13.820	13.800	0.02	0.002	0	0

Specific Gravity G=2.924

H_e=10cm
Volume of pipette =10ml
At room temp (27⁰C) µ =0.00855
Factor F =10⁵[3000*ȵ/ (G-1)*ɣ_w] =>F=1476
Diameter of the particle D =10^-5F [10/t] ^0.5

FOR % FINER

V=Volume of suspension =1000ml
m=Mass of dispersing agent present in a volume of 50ml =2g
M_d=Mass of sample taken =50g
M_D=Dry mass of sample in container/volume of pipette


N= [M_D-(m/V)]/ {M_d/V} *100
N= [(Dry mass/10) – (1/500)]*2000